Terahertz wave polarization conversion and unidirectional transmission device with double-layer dielectric-metal grating structure

Abstract

The invention discloses a terahertz wave polarization conversion and unidirectional transmission device with a double-layer participating medium-metal grating structure. The device comprises a metal grating layer, a medium substrate layer and a medium grating layer, wherein the metal grating layer and the medium grating layer are respectively positioned on two sides of the medium substrate layer; the medium grating layer is etched by a substrate material; an included angle between ridge orientation of medium grating and ridge orientation of metal grating is 45 degrees; the metal grating and the medium grating are sub-wavelength gratings; and the grating periods of the sub-wavelength gratings are smaller than the wavelength incident light. By the polarizing character of the metal grating layer and the artificial double refraction character of the medium grating layer, polarization conversion rate greater than 95% can be realized, and unidirectional transmission isolation greater than 30 db can also be realized. Due to the mode coupling effect between the metal grating layer and the medium grating layer, compared with a discrete component, the device has the characteristic that the emergent light transmissivity and working bandwidth are remarkably improved. The device is suitable for polarization conversion and unidirectional transmission of terahertz waves.

Description

technical field [0001] The invention belongs to the technical field of terahertz applications, and in particular relates to a terahertz wave polarization conversion and one-way transmission device with a double-layer dielectric-metal grating structure. Background technique [0002] Terahertz wave refers to the oscillation frequency in 10 12 Hz(1THz=10 12 Hz), this band is between microwave and light wave, and it is the intersection field of electronics and photonics. Terahertz wave technology mainly involves research on terahertz wave radiation sources, detectors, transmission, functional devices and related applications of terahertz waves, among which terahertz functional devices involve filtering, modulation, phase shifting, polarization conversion and other devices. Polarization conversion element is a device that changes the polarization state of incident light into another polarization state after passing through the device. It has important applications in the fields...

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Problems solved by technology

However, although these devices can achieve a one-way transmission isolation of more than 20dB, due to the high-order diffraction effect of the device, the forward transmission transmittance is very low and the working bandwidth is also very narrow, which affects the practicability of the device.

[0004] To sum up, on the one hand, the development of terahertz application systems has an urgent demand for the development of high-performance terahertz polarization conversion and unidirectional transmission devices; rate, isolation, insertion loss, and working bandwidth cannot meet the actual needs of the application system. It is urgent to develop terahertz polarization conversion and unidirectional transmission without external magnetic field, high polarization conversion rate, high isolation, low loss, and easy processing. device

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